package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

/**
 * Abstract decorator class of a DocIdSetIterator
 * implementation that provides on-demand filter/validation
 * mechanism on an underlying DocIdSetIterator.  See {@link
 * FilteredDocIdSet}.
 */
public abstract class FilteredDocIdSetIterator extends DocIdSetIterator {
    protected DocIdSetIterator _innerIter;
    private int doc;

    /**
     * Constructor.
     * @param innerIter Underlying DocIdSetIterator.
     */
    public FilteredDocIdSetIterator(DocIdSetIterator innerIter) {
        if (innerIter == null) {
            throw new IllegalArgumentException("null iterator");
        }
        _innerIter = innerIter;
        doc = -1;
    }

    /**
     * Validation method to determine whether a docid should be in the result set.
     * @param doc docid to be tested
     * @return true if input docid should be in the result set, false otherwise.
     * @see #FilteredDocIdSetIterator(DocIdSetIterator)
     */
    abstract protected boolean match(int doc) throws IOException;

    @Override
    public int docID() {
        return doc;
    }

    @Override
    public int nextDoc() throws IOException {
        while ((doc = _innerIter.nextDoc()) != NO_MORE_DOCS) {
            if (match(doc)) {
                return doc;
            }
        }
        return doc;
    }

    @Override
    public int advance(int target) throws IOException {
        doc = _innerIter.advance(target);
        if (doc != NO_MORE_DOCS) {
            if (match(doc)) {
                return doc;
            } else {
                while ((doc = _innerIter.nextDoc()) != NO_MORE_DOCS) {
                    if (match(doc)) {
                        return doc;
                    }
                }
                return doc;
            }
        }
        return doc;
    }

}
